Why is it that when I'm having sex with my wife, it always feels so unexciting? But when it's with other guys, she's like a h...

Why is it that when I'm having sex with my wife, it always feels so unexciting? But when it's with other guys, she's like a horny bitch in heat! Is it because my dick isn't good enough, or are those single men just incredibly big and irresistible? I watch her passionately kissing and licking each other's breasts, her wet pussy gushing, his huge, hard cock pounding into her cunt, fucking her hard and spurting hot semen! And me? I can only watch and masturbate to release my pent-up desire!